The present invention relates to air filter units for personal use and, in particular, to an air filter unit suitable for filtering the air directed to an individual seated on an aircraft.
Aircraft include a central air ventilation and filtering system which supplies all the passengers with a combination of recycled cabin air and fresh air taken in from the manifolds of the engines. These systems have the shortcoming of recycling pollutants and other irritants throughout the cabin. Since the tolerance level among passengers is quite variable, there exists a need for better filtration systems at least on an individual basis. Furthermore, when flying millions of passengers, 517 million U.S. bookings in 1994 alone, it is impossible to isolate or screen passengers who are sick or have health problems which may be transmittable to fellow travelers. By way of example, it was recently disclosed that a tuberculosis victim was aboard an international flight and four passengers did in fact become infected with tuberculosis.
Although the aircraft builders and the Federal Aviation Authority (FAA) set forth certain guidelines as to an aircraft's filter system, including the frequency between filter medium changes and cleaning valves and ducts, airlines often alter the schedule to suit their own standards and economies. Air filters for aircraft ventilation systems cost upwards of three hundred dollars each and each thorough cleaning of the aircraft's ducts and valves effectively reduces the amount of time an aircraft could be generating income. As a result, passengers do not always receive the very best air quality. The dangers of second hand smoke have been well documented, but it has only been within the recent past that smoking has all but been eliminated on domestic flights. Tobacco is obviously detected because of its smell. However, germs are colorless, odorless and create an even greater danger than tobacco smoke.
Examples of existing air filtering systems include passive filters which are inexpensive disposable filters found mainly in home heating and cooling systems. Other filters include electrostatic passive filters which create a static electrical charge to trap material passing through. Additionally, electrostatic precipitators use wires to electrically charge particles passing through the filter which are then attracted to polarized plates that act as magnets.
In addition, facial protection masks are available, such as dust and pollen masks, surgical masks and the like, it is not uncommon to see airline passengers wearing such masks when travelling in a closed air environment aircraft. Whereas these help prevent the spread of infectious bacteria and airborne germs caused by sneezing, coughing and other airborne viruses, their use is usually somewhat clumsy and restrict breathing, eating and conversing.
There is increased emphasis by the U.S. Surgeon General Office and The Environmental Protection Agency (EPA) to improve our health and clean up our air. Their goal is to make all public halls, buildings and confined spaces (this would include aircraft) as safe as possible from air-borne contaminants.
At the present time, there are no international or U.S. Governmental testing guidelines for air filters or their medium. However, the industry at large accepts the American Society for Heating Refrigeration and Air Conditioning (ASHRAE) testing procedures.
The results of ASHRAE 52.1 dust spot tests are reported in two distinct values, atmospheric dust spot efficiency and synthetic weight arrestance. Arrestance testing is mainly used by passive filter manufacturers to measure large (100 micron plus) dust particles (participates). However, ASHRAE 52.1 dust spot efficiency testing relates to the filter's meaningful ability to remove low micron to sub-micron size contaminants and bacteria.
The three levels of ASHRAE 52.1 dust spot efficiency are: low efficiency, which is less than 20 percent, medium efficiency, which is 25-60 percent, and high efficiency, which is 85-95 percent.
True high efficiency filter mediums are not cleanable. Once these filters load with contaminants, the restriction to air flow increases and necessitates timely filter changes before it becomes critical. The present invention contemplates the use of high efficiency filter mediums. Consequently, the present air filter unit must be manufactured to be disposable or contain an easy means for filter replacement.
In view of the shortcomings of filtering systems currently in use in aircraft, a need exists for a supplemental air filter that can conveniently be used aboard aircraft. The present invention provides such a filter.